1. Field of the Invention
The present invention relates to a security paper with built-in rigid members, and more particularly, to such security paper that can be readily used in large production paper webs avoiding contact with the knives that cut the web into sheets and smaller portions suitable for the intended end product.
2. Description of the Related Art
A number of techniques have been used to code security paper, such as the paper used for legal tender bills and negotiable instruments in general that carry a nominal value superior to their intrinsic value. Most of these techniques involve the use of water marks and other impressions on the paper that attempt to make it unique in order to frustrate the efforts of wrongdoers that try to duplicate these techniques. The use of a rigid body, preferably with ferromagnetic characteristics, inside the paper creates an unsurmountable burden for these wrongdoers, specially if the rigid segment can be uniquely coded.
The insertion of a rigid body in a paper web faces a number of problems. One of these problems is associated with the marked difference in coefficients or modulus of expansion (elasticity) of the paper being formed and the rigid body being inserted. This is further complicated by the demands imposed by the current production processes of large quantities of security papers such as the one used for printing money bills, stocks, bonds, checks, etc., which require the precise alignment of these rigid segments in relatively large sheets for subsequent cutting and printing operations.